Monophyly of some North American species ofRamalinaand inferred polyketide synthase gene function

Abstract

Ramalina thrausta (Ach.) Nyl., Ramalina roesleri (Hochst. Ex Schaerer) Hue, and Ramalina dilacerata (Hoffm.) Hoffm. are three common North American species that have not been placed in a phylogeny and are sympatric in their distribution leading to uncertainty about monophyly. Species characters include secondary metabolites (polyketides) in Ramalina that may be both hereditary and influenced by environmental conditions, but little is known about the function of polyketide synthase (PKS) genes. The main goal of this study was to examine the monophyly among some of the more common species in northern North America and secondarily to compare potential PKS gene function with the phylogeny. Nucleotide sequences of two genes, the internal transcribed spacer 1 of ribosomal DNA and the mitochondrial small subunit, were used to infer a phylogeny. Gene function was inferred from three PKS genes by the ratio of nonsynonymous to synonymous substitutions (dN:dS) ratios. Although seven species of Ramalina are highly supported in monophyletic clades, two other species form clusters with low support: Ramalina americana Hale is paraphyletic, and Ramalina pollinaria (Westr.) Ach. is polyphyletic. Three PKS genes were inferred to be functional but were not present in all samples. Functional PKS genes could enable adaptation to new habitats and facilitate species diversification.

Ramalina europaeaandR. labiosorediata, two new species of theR. pollinariagroup (Ascomycota:Ramalinaceae), and new typifications forLichen pollinariusandL. squarrosus

“…The ITS barcoding locus has been recommended for Fungi (Schoch et al 2012) and has been successfully employed in several studies of species delimitation and population genetics in the genus Ramalina (Groner & LaGreca 1997; LaGreca 1999; Stocker-Wörgötter et al 2004; Ohmura et al 2008; Sérusiaux et al 2010; Francisco de Oliveira et al 2012; Timsina et al 2012; Del Campo et al 2013; Hayward et al 2014). Thus, while some workers such as Kashiwadani & Moon (2002) accept R. pollinaria in a broad sense, phylogenetic studies on North American representatives using ITS (Timsina et al 2012) suggest that this is a polyphyletic entity. Ohmura et al (2008), after revision of the three phenotypically similar species R. pollinaria , R. yasudae and R. sekika , confirmed the status of the last two taxa as separate from R. pollinaria in East Asia, and they are actually not closely related to R. pollinaria .…”

A molecular phylogenetic evaluation of theRamalina siliquosacomplex, with notes on species circumscription and relationships withinRamalina

“…2004; Timsina et al . 2012; Pérez-Vargas & Pérez-Ortega 2014; Gasparyan et al . 2017) have all indicated that R .…”

“…(2004) and Timsina et al . (2012) that Ramalina species containing medullary products are derived. By contrast, all Ramalina species that lack these medullary products are found in clades K, L, M and N. Furthermore, interestingly, compared to all but one of the species ( R .…”

“…2010; Timsina et al . 2012; Pérez-Vargas & Pérez-Ortega 2014; Gasparyan et al . 2017), and of species complexes within Ramalina (Groner & LaGreca 1997; LaGreca 1999; Ohmura et al .…”

“…To paraphrase Timsina et al . (2012), it appears that molecular data generated thus far for Ramalina are best used for species diagnosis rather than phylogenetic reconstruction.…”